Self-propelled windrowers typically include a main frame supported on a pair of front wheels, which are separately driven hydrostatically so as to afford steering to the windrower by driving the wheels at different speeds, and a pair of rear wheels which are mounted to opposite ends of a rear axle so that they pivot about an upright caster axis. Some windrowers are capable of delivering conditioned crop to one side of the vehicle to form a windrow in a region which may be located at least partially in the track behind the front wheel at that side of the vehicle in order to group the windrow with a previously formed windrow laid down along a path at the center of the vehicle between the front and rear pairs of wheels. The axle sections to which the rear wheels are telescopically mounted within a remaining middle section of the rear axle and are fixed in selected positions so as to change the distance between the rear wheels, with the rear wheel on the discharge side of the vehicle being adjusted inwardly towards the center of the vehicle so that the adjusted wheel will not run upon the crop windrow. An example of such a self-propelled windrower is disclosed in U.S. Pat. No. 7,028,459.
A hydraulic steering assist system (see U.S. patent application Ser. No. 11/957,800, filed on 17 Dec., 2007 and assigned to the assignee of the instant application) has been developed for steering the rear wheels of a self-propelled windrower in conjunction with the steering of the driven front wheels in order to give an operator more control over the self-propelled windrower when operated at relatively high road or transport speeds. The steering cylinders of this steering assist system are respectively secured to cylinder mounting assemblies respectively fixed at opposite end locations of a tubular middle section of the rear axle and into opposite ends of which opposite end sections of the axle are telescopically received for adjustment, with the rod ends of the cylinders being coupled to steering arms respectively fixed to top end regions of the upright spindles of the caster-mounted wheels. A drawback of this assist system is that, while the rear axle is disclosed as being adjustable in length, no provision is made for adjusting the position of the steering assist cylinder in order to accommodate for the change in axle length, and, hence, the change in the distance between the steering arm at the top of the caster spindle and the fixed steering cylinder.
The problem to be solved is to provide a simple cylinder mounting structure for resisting steering assist cylinder reaction loads and for also allowing the cylinder to be repositioned for maintaining steering function when the axle length has been adjusted.